Conical set screw

Abstract

The present invention relates to a conical fixation helix and a capsule (e.g. a leadless pacing, sensing and / or communication device) comprising the conical fixation helix for fixing a pacing device at a patient tissue. The conical shape of the fixation helix allows a better attachment of the pacing device to the patient tissue and squeezes the patient tissue towards the tip electrode of the capsule.

Description

Technical Field

[0001] This invention relates to the field of electrode fixation structures for pacing, sensing and / or communication devices (e.g., capsules, lead devices and / or leadless electrode devices) for cardiac or other pacing and / or sensing systems, such as, but not limited to, left bundle branch (LBB) pacing, cardiac resynchronization or tachycardia (“tachycardia”) systems. Background Technology

[0002] The cardiac conduction system includes the sinoatrial node (SAN), atrioventricular node (AVN), His bundle, bundle branches, and Purkinje fibers. The heartbeat originates in the SAN, which can be considered the heart's natural "pacemaker." Electrical impulses originating from the SAN cause atrial contractions. This signal is conducted to the ventricles via the AVN, where conduction is itself delayed to allow the atria to stop contracting before the ventricles begin to contract, thus providing proper AV synchronization. Electrical impulses are conducted from the AVN to the ventricular myocardium via the His bundle, bundle branches, and Purkinje fibers.

[0003] Patients with conduction system abnormalities (such as poor AV junction conduction or SAN dysfunction) may receive implantable medical devices (IMDs), such as pacemakers, to restore a more normal heart rhythm and AV synchronization. Some types of IMDs, such as pacemakers, implantable cardioverter-defibrillators (ICDs), or cardiac resynchronization therapy (CRT) devices, deliver therapeutic electrical stimulation to the patient's heart via electrodes placed in or adjacent to the heart on one or more implantable endocardial, epicardial, or coronary vein leads. This therapeutic electrical stimulation can be delivered to the heart in the form of pulses or electric shocks for pacing, cardioversion, or defibrillation. In some cases, IMDs can sense the heart's inherent depolarization and control the delivery of therapeutic stimulation to the heart based on this sensing.

[0004] Since the 1950s, the right ventricle (RV) has been the most commonly used site for delivering artificial pacemaker stimulation, with both the RV tip and septal location available for stimulation. The pacing lead, implanted via the superior vena cava, passes through the tricuspid valve and, using a simple curved core, delivers stimulation upwards to the pulmonary valve. Unless the lead tip arches posteriorly during screw deployment, the lead tip is more likely to become attached to the anterior or free wall. Left bundle branch pacing (LBBP) has emerged as an alternative method for delivering physiological pacing to achieve electrical synchronization of the left ventricle (LV), particularly in patients with subnodal conduction block and / or LBBB. The proximal LBB crosses the LV septum and spreads out, forming a wider pacing target compared to the His bundle. An LBBP technique using a ventricular transseptal approach (i.e., pacing the LV from the RV) has been developed. LBBP has been reported to provide a low pacing threshold and large R waves, and, because it targets the distal conduction system, has a theoretically lower risk of distal conduction block.

[0005] After determining the initial location of the LBBP on the right surface of the ventricular septum, a helical fixation element is screwed into the LV septum, for example, by puncturing the tissue with the distal end of the helical fixation element (fixation spiral). The depth of insertion into the LV septum can be determined by one or more of the following: observed changes in the V1 lead notch, sheath angiography, fulcrum sign, and impedance monitoring. By applying torque, the pacing electrode is slowly advanced to the determined depth of the septum (e.g., approximately 8 to 12 mm) while avoiding LV-side perforation of the septum. Finally, LBB capture is confirmed based on acceptable pacing parameters. Such confirmation can be based on at least one of the following: pacing morphology of the RBBB pattern, recording of the LBB potential, peak stimulation of the LVAT (which shortens abruptly with increasing output or remains shortest and constant at low and high output), selective and non-selective LBBP, and recording of retrograde or forward LBB potentials during pacing.

[0006] The ends of pacing or tachycardia leads are typically designed to avoid the risk of septal perforation. They may also be equipped with soft ends (made of, for example, silicone) to increase the stopping surface. That is, when the helical fixing element or electrode (hereinafter referred to as the "helix") engages with (e.g., screwed into) (cardiac) tissue, the tissue is pushed toward the soft end to stop the helix from rotating and advancing further within the tissue. The length of the helix can be limited to, for example, an effective length of about 2 mm.

[0007] In lead-based LBBP techniques, common features of the implantation or placement process include transvenous access, placement of the pacing lead through the interventricular septum into the subendocardium of the LBB region, and confirmation of LBB capture as described above.

[0008] As an alternative, leadless techniques have been developed in which a leadless medical device (e.g., a capsule) with a spiral, for example, is implanted in the apex region, more preferably in the lower septum, to limit the risk of perforation of a thin apex. The capsule is typically 35 mm in length, including the spiral (2 mm). This capsule can be delivered via a vascular catheter introduced through the femoral artery.

[0009] Pacemakers (lead devices and leadless devices) require a fixation system that ensures reliable attachment to the patient’s tissues and proper electrical connection. Summary of the Invention

[0010] The purpose of this invention is to provide an improved electrode fixing system.

[0011] This objective is achieved by the fixed helix as described in claim 1 and the pacing device as described in claim 4.

[0012] Therefore, the conical shape of one or more distal coils, or all coils, of the proposed fixed helix can be configured to compress the tissue toward the distal electrode of the pacemaker upon insertion into the tissue. Thus, the attachment of the distal portion of the pacemaker to the myocardium or other patient tissue can be safely and stably achieved without causing serious damage to the heart or other body parts. This enables reliable attachment with improved electrical connection to the patient tissue.

[0013] According to the first option, the diameter of the conical ring can increase with respect to the distance in the distal direction in a linear, quadratic, cubic, quartic, elliptic, or exponential relationship.

[0014] According to a second option that can be combined with the first option, the fixed helix may further include a non-insulated end electrode at the distal end of the fixed helix.

[0015] According to a third option, which can be combined with the first or second option, the coil of the fixed helix can be configured to compress the tissue toward the terminal electrode of the pacing device when it is screwed into the tissue.

[0016] According to the fourth option, the maximum diameter of the coil at the distal end of the fixed helix can be configured to match the diameter of the cylindrical housing of the pacing device.

[0017] It should be further understood that the preferred embodiments of the present invention may also be any combination of the dependent claims or the above embodiments and the corresponding independent claims.

[0018] These and other aspects of the invention will be shown and illustrated with reference to the embodiments described below. Attached Figure Description

[0019] In the following figures: Figure 1 The heart is schematically shown, with corresponding placement options for leaded and leadless devices for ventricular transseptal LBB pacing. Figure 2 A side view of a conical fixed helix having a linear conical shape according to a first embodiment is schematically shown; Figures 3A to 3C A cross-sectional side view of different conical fixed helices having corresponding elliptical, quadratic, and exponential conical shapes according to the second to fourth embodiments is schematically shown; Figure 4 A schematic perspective top view of a wireless capsule having a double-ringed end electrode and a conical helix according to a fifth embodiment is shown; and Figure 5 A perspective side view of a leadless pacemaker with a conical fixed helix according to a sixth embodiment is shown schematically. Detailed Implementation

[0020] Various embodiments of the invention are now described based on leadless medical pacing, sensing, and / or communication devices (e.g., capsules) with tapered fixed electrodes. While the invention is particularly advantageous in the context of leadless pacing devices, it is not limited thereto and can be used in conjunction with any type of pacing, sensing, and / or communication lead and / or other pacing types and / or other application sites requiring placement of pacing devices within body tissue.

[0021] It is worth noting that throughout this disclosure, only those elements, parts, components, and / or devices related to the proposed pacing device and placement operation are shown in the accompanying drawings. For the sake of brevity, other elements, parts, components, and / or devices may have been omitted. Furthermore, components designated with the same reference numerals or numbers are intended to have the same or at least similar functions, and therefore their functions will not be described further below.

[0022] Furthermore, throughout this disclosure, the terms "proximal" and "distal" are used to indicate the distance from the operating tip (reference point) of the pacemaker, where a physician or other user controls the rotation process. Proximal refers to being closer to the operating tip, while distal refers to being farther away (larger distance) from the operating tip.

[0023] As used herein, “leadless” means that a medical device (such as a pacing, sensing, and / or communication device) does not have any one or more leads extending from the medical device to the patient’s heart. Some leadless devices can be introduced via a vein, but once implanted, such devices have no (or may not include) any transvenous leads and can be configured to provide cardiac treatment without the use of any transvenous leads.

[0024] As used in this article, "axial" direction or length refers to the longitudinal axis of the pacemaker and / or the fixation spiral used to secure the pacemaker to the patient's tissues.

[0025] Figure 1 A heart with an inserted lead device 200 is schematically shown, in which the pacing lead tip 20 is placed for transseptal ventricular LBBP. Furthermore, for comparison, a leadless device (capsule) 400 is also shown, its helix 300 not yet inserted into the septum 24. Thus, LV pacing can be performed from the RV via a transseptal ventricular approach. The placement of the pacing lead tip 20 can be based on the procedure briefly explained in the above-mentioned introduction. LBBP can be defined as the capture of the LBB (i.e., the left bundle trunk or its proximal branch), typically at low output (e.g., <1.0 V / 0.4 ms) of the septal myocardium.

[0026] It is worth noting that, with Figure 1 Conversely, the pacing lead tip 20 and the leadless device 400 are not intended for simultaneous use. They can be used as alternatives depending on the patient's condition / symptoms.

[0027] As described in the introduction, in normal cardiac function, the heartbeat begins on the heart itself, thanks to the SAN, located at the top of the right atrium (RA) (i.e., the neck / head region facing the body) and setting the frequency of the heart's contractions. It emits electrical impulses that are transmitted through the muscular walls of both atria. These impulses cause atrial contractions. The impulses are then transmitted to another knot inside the heart—the AVN. This knot is located in the lower part of the RA, within the subendocardial layer of the atrial septum wall, which separates the RA from the left atrium (LA). Once the impulses from the SAN reach the AVN, they are transmitted to the conduction fibers, which propagate downwards along the central wall of the heart. The impulses then branch and propagate upwards to the LV and RV, causing them to contract, with a natural delay between the contractions of the LV and RV (ventricular systole).

[0028] The vital components of the cardiac conduction system are located within septum 24. The His bundle proceeds subendocardially, descending approximately 1 cm to the right of septum 24, before dividing into the LBB and RBB. The LBB continues descending to the right of septum 24, while the LBB crosses to reach the left side and branches into the anterior and posterior fasciculi.

[0029] Normally, the activation of the sinus rhythm controls the heart rhythm. Abnormalities in sinus rhythm can lead to arrhythmias, which are abnormalities in the rate, rhythm, origin, and conduction of cardiac electrical impulses. When there is a disorder in the conduction fibers of a specific ventricle, the repolarization wave must then travel through slower intermuscular conduction to reach the ventricle. Classic disorders associated with conditions involving different conduction branches include LBBB and RBBB. An electrocardiogram (ECG), obtained through the insertion of a lead device, is used to measure and record the heart's electrical activity, thus providing important information about cardiac function. ECG has been used as a standard diagnostic tool for analyzing arrhythmias.

[0030] In one or more embodiments, the pacing device for bundle pacing is a leadless device that can be operatively connected to electrodes positioned near the septum without the use of wires when the device housing is placed in the RV. However, it should be noted that in embodiments, the pacing device (e.g., a capsule or lead) may also be placed in the RA. The helix can be wirelessly coupled to the housing of the leadless device without the need for a wire between the electrode and the housing. The leadless device (i.e., the implemented medical pacing device) can sense electrical signals accompanying cardiac depolarization and repolarization via a terminal electrode at the distal end of the body of the leadless device and optionally via a terminal electrode fixing the helix. In some instances, the leadless device can deliver pacing pulses to the heart based on electrical signals sensed within the heart. The electrode configuration for sensing and / or pacing can be unipolar (e.g., in the case of a lead device) or multipolar (e.g., in the case of a leadless capsule or lead device). The lead assembly can be a conventional lead with a single pole (monopolar) that is connected to the housing / shell of a pacemaker / defibrillator, where the housing / shell becomes a second pole for sensing and / or pacing.

[0031] Leadless devices can also deliver defibrillation and / or cardioversion therapy via one or more electrodes based on detected cardiac arrhythmias (such as ventricular fibrillation), for example, by delivering defibrillation therapy to the heart in the form of electrical pulses. In some instances, leadless devices can be programmed to deliver progressive therapy, for example, with pulses of increasing energy levels until the fibrillation stops. For this purpose, leadless devices can employ one or more fibrillation detection techniques known in the art to detect fibrillation.

[0032] The leadless device may include an intracardiac housing comprising sensing circuitry operatively coupled to electrodes (i.e., distal electrodes) and configured to sense one or both of atrial and ventricular events using those electrodes. Furthermore, the housing may include an electrical pulse generator coupled to bundle branch pacing electrodes (i.e., distal electrodes), configured to generate and deliver bundle branch pacing electrical pulses to the patient's heart based on one or both of atrial and ventricular events using the bundle branch pacing electrodes. The housing may also include a communication interface configured to receive control signals. The leadless device may further include a controller disposed within the housing and operatively coupled to the pulse generator for controlling the delivery of bundle branch pacing pulses to the patient's heart in response to the received control signals.

[0033] The embodiments of the conical fixation spiral of the pacemaker (e.g., leadless device) described below are configured to stabilize the attachment of the terminal electrode and improve its contact efficiency during fixation by the conical fixation spiral.

[0034] Figure 2 A side view of a conical fixed helix 50 having a linear conical shape according to a first embodiment is shown schematically.

[0035] like Figure 2 As shown, the diameter of the spiral coil of the conical fixed helix 50 is in the distal direction ( Figure 2 The distance from the capsule (not shown) increases linearly from right to left to achieve a conical shape, as indicated by the dashed line. The total length (or height) of the fixed helix can range from 1 mm to 13 mm.

[0036] This conical shape, with a diameter that widens towards the distal end and features a spiral coil, allows the distal end of the pacing device (e.g., a leadless capsule) to better attach to myocardial tissue or other patient tissue, while simultaneously pressing the tissue toward the distal electrode of the pacing device.

[0037] The number of coils in the conical fixation helix 50 depends on its function, i.e., whether it is used solely for fixation (fewer coils) or for both fixation and pacing / sensing via its own terminal electrode (more coils). Practical examples of the number of coils range from 1 to 16, with only one or a few distal coils being conical, while the remaining coils in the proximal portion of the fixation helix 50 may have a constant diameter.

[0038] Additionally, the ratio of the distal diameter to the proximal diameter of the cone-shaped fixed spiral depends on whether the distal portion of the pacemaker (e.g., capsule) should be inserted (implanted) into the patient's tissue (perforation). Practical examples of this ratio may range from 1.05 to 4. The spiral diameter may also depend on the capsule diameter, and when the capsule diameter ranges from 4 mm to 8 mm, the spiral diameter can range from 2 mm to 8 mm, where the ratio between the spiral diameter and the capsule diameter can range from 0.5 to 1.

[0039] The spiral coil of the conical fixed helix 50 can have a polygonal (e.g., quadratic or rectangular) or circular cross-sectional shape.

[0040] Figures 3A to 3C A cross-sectional side view of different conical fixed helices with other conical shapes is schematically shown.

[0041] Figure 3A The conical fixed helix according to the second embodiment is schematically shown, wherein the diameter of the helical coil increases elliptically in the distal direction.

[0042] Figure 3B The conical fixed helix according to the third embodiment is schematically shown, wherein the diameter of the helical coil increases in a quadratic function manner in the distal direction.

[0043] Figure 3C The conical fixed helix according to the fourth embodiment is schematically shown, wherein the diameter of the helical coil increases exponentially in the distal direction.

[0044] Other conical shapes with other functional relationships (such as cubic, quartic, etc.) can also be implemented.

[0045] Figure 4 A schematic perspective top view of the distal portion of a wireless capsule according to a fifth embodiment is shown, the distal portion having a distal electrode 20 and a conical helix 50, which can be used for cardiac surface stimulation, such as RV septal stimulation.

[0046] It should be noted that for LBB applications, the conical spiral 50 can be longer and have more turns.

[0047] To improve the quality and / or integrity of the electrical contact between one or more output connections / interfaces (not shown) of the leadless capsule and the end electrode 20, a permanent and robust connection can be established (e.g., by screwing, welding, crimping, etc.). Furthermore, if the conical helix 50 also includes the end electrode, the proximal portion of the conical helix 50 can be mechanically secured to the housing 54 of the leadless capsule and can then optionally be connected to internal electronic circuitry (e.g., via feedthrough technology, which also ensures an hermetically sealed housing).

[0048] As described above, at least part of the conical shape of the conical helix 50 allows for better attachment of the distal end of the pacing device (e.g., a leadless capsule) to myocardial tissue or other patient tissue, while compressing the tissue toward the distal electrode 20 of the pacing device.

[0049] The maximum diameter of the coil at the distal end of the conical helix 50 can be selected to match (substantially) the diameter of the capsule shell 54, thereby facilitating smooth implantation of the capsule during tissue perforation. Furthermore, the coil of the conical helix 50 may include an insulating surface to prevent undesirable electrode function. The insulating surface can be achieved by covering the coil with a dielectric or other insulating material.

[0050] In addition, a protective ring with a radially protruding protective element 52 can be provided at the proximal end of the conical spiral 50 to prevent the conical spiral 50 from spiraling out of the patient's tissue along with the capsule.

[0051] Alternatively, a non-conductive (e.g., non-metallic) insulating ring 56 may be provided to insulate the end electrode 20 from the conical helix 50.

[0052] like Figure 4 The leadless capsule shown can be used for septal RV stimulation, wherein the conical spiral 50 is screwed into the anterior wall or free wall of the septum. However, Figure 4 The leadless capsule can also be used for other placements, such as tip RV stimulation or RA stimulation.

[0053] Optionally, to provide additional cathode functionality to the LBBP, the spiral coils of the distal segment of the conical helix 50 may be left uninsulated by any non-conductive covering or isolation. In one example, the surface of the spiral coils of the uninsulated distal segment may be coated with classic TiN (titanium nitride) to optimize electrical properties. Furthermore, the distal segment may be configured to provide X-ray visibility to help physicians precisely position the cathode within the width of the septum.

[0054] In this configuration, if two terminal electrodes are used (one at the distal end of the conical helix 50 and the other at terminal electrode 20), terminal electrode 20 can be used as an (additional) RV cathode. If terminal electrode 20 is used in combination with the helical terminal electrode, independent LV / RV pacing with a controlled delay between stimulations of the two chambers can be implemented.

[0055] The conical helix 50 can be made using, for example, laser tube cutting to allow the "line" structure of the helical coils to have a tapered, variable diameter along the coils of the helical structure. Laser tube cutting is a process and technique used to cut tubes, structural shapes, or channels. This process cuts these objects to the desired length. It can also cut cavities or specific shapes (designs) into tubes. It is a precise cutting technique. It can also be used with a wide variety of materials in all shapes and sizes. There are many types of laser tube cutting equipment to meet different cutting needs. 3-axis laser tube cutting machines perform three-dimensional cutting.

[0056] Alternatively, the conical helix 50 can be made using a classic winding of one or more insulated wires (e.g., the inner conductor of a lead-in device, which has a winding of 4 to 6 individual wires).

[0057] Figure 5 A schematic perspective side view of a leadless capsule (as an example of a lead device or pacing device) according to a sixth embodiment is shown, in which the conical helix 50 of the above embodiment is implemented.

[0058] The leadless capsule includes a housing 130 having or defining an outer wall 135 (a cylindrical outer wall shown in the figure) extending from a distal end region 132 of the housing to a proximal end region 134 of the housing. The housing 130 may enclose electronic circuitry configured to perform single-chamber or multi-chamber cardiac therapy, including atrial and ventricular cardiac electrical signal sensing and pacing of the atrial and ventricular chambers. A delivery tool interface member 126 may be disposed on the proximal end region 134 of the housing.

[0059] Furthermore, the distal fixation and electrode assembly 136 may be connected to the distal end region 132 of the housing. The distal fixation and electrode assembly 136 may include an electrically insulating distal member 172 coupled to the distal end region 132 of the housing. The electrically insulating distal member 172 includes a terminal electrode 20 and a conical helix 50 extending from the distal end region 132 of the housing. The conical helix 50 extends longitudinally from the distal end region 132 of the housing and may be coaxial with the longitudinal central axis 131 of the housing 130.

[0060] The conical helix 50 may include an electrically insulating rod and act as a fixing member. It may optionally include a distal cathode terminal electrode element (not shown). The proximal end region of the rod of the fixing helix 50 may be directly coupled to the insulating distal member 172. The helical rod may be coated with an electrically insulating material, such as parylene, to avoid sensing or stimulating cardiac tissue along its axial length.

[0061] The terminal electrode 20 can be used as a cathode electrode for delivering ventricular pacing pulses and sensing ventricular electrical signals, using a proximal housing-based electrode 124 as a return anode. The proximal housing-based electrode 124 can be an annular electrode surrounding the housing 130 and can be defined by an uninsulated portion of the longitudinal sidewall 135. Other non-electrode portions of the housing 130 can be coated with an electrically insulating material.

[0062] In embodiments, multiple cathodes (e.g., the terminal electrodes of the conical helix 50 and terminal electrode 20) may be used for bipolar or multipolar sensing or pacing. These multiple cathodes may include tissue-penetrating electrodes (e.g., the conical helix 50) and non-tissue-penetrating electrodes (e.g., terminal electrode 20) located at the periphery of the insulating distal member 172. The insulating distal member 172 may define a distally facing surface 138 of the capsule and a circumferential surface 139 surrounding the capsule and abutting the longitudinal sidewall 135 of the shell.

[0063] As the conical helix 50 advances into the heart tissue, the distal electrode 20 comes into close contact with the heart tissue surface to deliver pulses and / or sense electrical signals generated by the patient's heart. The distal electrode 20 can be coupled to a treatment delivery circuit and sensing circuit enclosed by the housing 130 to act as a cathode electrode for delivering atrial pacing pulses and sensing atrial electrical signals (e.g., P waves), used in combination with the proximal housing-based electrode 124 (as a return anode). Switching circuitry included in the sensing circuitry can be activated under the control of control circuitry to couple the distal electrode 20 to an atrial sensing channel. Switching circuitry included in the treatment delivery circuitry can be activated under the control of control circuitry to couple the distal electrode 20 to the atrial pacing circuitry.

[0064] In the above embodiments, the housing of the leadless device (e.g., a leadless pacemaker) can be made of a plastic material such as polyetheretherketone (PEEK) due to its high biocompatibility and excellent mechanical rigidity. Alternatively, the housing of the leadless device can also be made of titanium (to achieve, for example, X-ray transparency, weldability, desired mechanical and biological properties), and coated with an insulating coating such as parylene or ethylene tetrafluoroethylene (ETFE). Optionally, an additional safety insulating layer can be added to the housing to enhance electrical insulation and improve the housing's abrasion resistance.

[0065] In summary, a conical fixation spiral and a capsule (e.g., a leadless pacing, sensing, and / or communication device) including the conical fixation spiral are described for securing a pacing device to patient tissue. The conical shape of the fixation spiral allows for better attachment of the pacing device to the patient tissue and compresses the patient tissue toward the terminal electrode of the capsule.

[0066] Although the invention has been shown and described in detail in the accompanying drawings and the foregoing description, such showing and description should be considered illustrative or exemplary rather than limiting. The invention is not limited to the disclosed embodiment of the terminal electrode with a double-ring configuration. The conical shape of any other conical helix is ​​intended to be covered. Conical helices can be applied to various types of pacing devices (e.g., bradycardia or tachycardia leads with multi-chamber, coaxial, or coradial structures) and cardiac pacing or sensing systems to reduce the space required before and / or after insertion of the fixed helix.

[0067] More specifically, the conical helix can be used in conjunction with various lead devices of different designs, which may have multi-cavity, coaxial, and co-radial structures, for use as tachycardia leads or bradycardia leads, and can provide a central cavity for the lead passage. The coaxial lead has an inner conductor that extends downward along the length of the lead to the terminal electrode (helix), i.e., the cathode, which is arranged to provide a coil configuration for the central cavity, for example, to allow the lead to pass through during implantation. In conjunction with the described embodiments, the conical helix can also be configured as a retractable helix.

[0068] Furthermore, the conductor system with the proposed conical helix can be configured to provide improved torque capability, i.e., the ability to safely and accurately transmit torque to the conical helix (e.g., full conductor body torque) and compatibility with core drive to simplify manipulation (e.g., by push transmission). In one instance, conductors of the same diameter with compatible screw-in cores (screwdriver cores) can be provided.

[0069] The pacemaker with the proposed conical helix can be configured to adapt to or be compatible with IS1, IS4 (low voltage) or DF4 (high voltage) connectors.

[0070] By studying the accompanying drawings, the disclosure, and the appended claims, those skilled in the art can understand and implement other variations of the disclosed embodiments in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plural. The fact that certain measures are recited in mutually different dependent claims does not mean that combinations of these measures cannot be used advantageously. The foregoing description details certain embodiments of the invention. However, it should be understood that the invention can be implemented in many ways, and is therefore not limited to the disclosed embodiments, no matter how detailed the foregoing may appear in the text. It should be noted that the use of specific terms in describing certain features or aspects of the invention should not be construed as implying that such terms are redefined herein to limit any particular characteristic of the invention's features or aspects associated with that term.

Claims

1. A fixed helical body (50) for a pacing, sensing and / or communication device, the fixed helical body (50) being configured to be mounted on a distal end of the device and having one or more distal conical coils, the distal conical coils increasing in diameter in the distal direction to obtain a conical shape.

2. The fixed helical body (50) according to claim 1, wherein, The diameter of the conical ring increases with respect to the distance in the distal direction in a linear, quadratic, cubic, quartic, elliptic, or exponential relationship.

3. The fixed helix (50) according to claim 1 or 2, further comprising a non-insulated end electrode at the distal end of the fixed helix (50).

4. A pacing, sensing and / or communication device comprising a fixed helical body (50) as described in any of the preceding claims.

5. The device according to claim 4, further comprising a terminal electrode (20), wherein, The spiral coil of the fixed spiral (50) is configured to compress the tissue toward the terminal electrode (20) when screwed into the tissue.

6. The apparatus according to claim 5, wherein, The maximum diameter of the spiral coil at the distal end of the fixed helix (50) is configured to match the diameter of the cylindrical housing (54) of the device.

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